DEV Community

Aisalkyn Aidarova
Aisalkyn Aidarova

Posted on

Terraform Lab 2 – Deploy Multiple Servers Using for_each

#devops #aws #terraform #tutorial

Goal
Instead of using count, deploy multiple servers using a map configuration.

Each server will have:

  • different name
  • different instance type

This is very common in real DevOps infrastructure.

Project Structure

create a new folder.

mkdir terraform-foreach-lab
cd terraform-foreach-lab
Enter fullscreen mode Exit fullscreen mode

Create files

touch main.tf variables.tf outputs.tf terraform.tfvars
Enter fullscreen mode Exit fullscreen mode

Project structure

terraform-foreach-lab
│
├── main.tf
├── variables.tf
├── outputs.tf
└── terraform.tfvars
Enter fullscreen mode Exit fullscreen mode

variables.tf

copy everything below.

variable "aws_region" {
  description = "AWS region"
  type        = string
}

variable "servers" {

  description = "Server configuration"

  type = map(object({

    instance_type = string
    name          = string

  }))

}
Enter fullscreen mode Exit fullscreen mode

Concept students learn:

  • map
  • object
  • infrastructure configuration

terraform.tfvars

define servers.

aws_region = "us-east-2"

servers = {

  web = {
    instance_type = "t2.micro"
    name          = "web-server"
  }

  api = {
    instance_type = "t2.micro"
    name          = "api-server"
  }

  worker = {
    instance_type = "t2.micro"
    name          = "worker-server"
  }

}
Enter fullscreen mode Exit fullscreen mode

Now Terraform knows 3 servers must be created.

main.tf

copy the full file.

provider "aws" {

  region = var.aws_region

}

########################################
# DATA SOURCE
########################################

data "aws_ami" "amazon_linux" {

  most_recent = true

  owners = ["amazon"]

  filter {

    name = "name"

    values = ["amzn2-ami-hvm-*-x86_64-gp2"]

  }

}

########################################
# EC2 INSTANCES
########################################

resource "aws_instance" "servers" {

  for_each = var.servers

  ami           = data.aws_ami.amazon_linux.id

  instance_type = each.value.instance_type

  tags = {

    Name = upper(each.value.name)

    Role = each.key

  }

}
Enter fullscreen mode Exit fullscreen mode

Important concepts here:

Concept Explanation
for_each creates multiple resources
each.key map key
each.value map value
function upper()

outputs.tf 

output "instance_ids" {

  value = {

    for server, instance in aws_instance.servers :

    server => instance.id

  }

}

output "public_ips" {

  value = {

    for server, instance in aws_instance.servers :

    server => instance.public_ip

  }

}
Enter fullscreen mode Exit fullscreen mode

learn:

  • for expressions
  • returning structured outputs

Run the Lab

Initialize Terraform

terraform init
Enter fullscreen mode Exit fullscreen mode

Preview infrastructure

terraform plan
Enter fullscreen mode Exit fullscreen mode

Create infrastructure

terraform apply
Enter fullscreen mode Exit fullscreen mode

Result

Terraform creates 3 servers

web-server
api-server
worker-server
Enter fullscreen mode Exit fullscreen mode

Example output

public_ips = {
  web    = 3.18.200.21
  api    = 18.220.45.11
  worker = 3.144.22.90
}
Enter fullscreen mode Exit fullscreen mode

What Learn in Lab 2

Concept Used
map server definitions
object structured configuration
for_each multiple resources
each.key map key
each.value map values
functions upper()
data source AMI lookup
outputs structured output

Top comments (0)